Seed germination medium

ABSTRACT

This invention provides a seed germination medium comprising an upper layer formed from a tissue paper having a weight of approximately 10-30 g/m 2 , the tissue paper being coated or impregnated with a waterproofing agent such that the tissue paper is permeable to gases but substantially impermeable to water in liquid form; a lower layer formed from a water-absorbent biodegradable material; seeds being disposed beneath the upper layer; and the upper layer optionally having a plurality of perforations therein to assist disruption of the upper layer to enable seedlings germinating from the seeds to grow therethrough.

This invention relates to a seed germination medium for encouraging thegermination and establishment of seeds, especially in hostileenvironments, where water, nutrients, climate, chemical contaminationand soil conditions may be limiting factors.

BACKGROUND OF THE INVENTION

Desertification, salination and soil erosion are significant andincreasing problems in many parts of the world. They are typicallycaused by climatic change, rapidly increasing population, shortage ofwater and loss of agricultural land to development. This process oftenplaces unprecedented pressure for increased productivity from adiminishing and non-renewable land resource. This often leads tocontamination of the soil with salts (from contaminated irrigationwater, ground water, and fertiliser use) which eventually makes itimpossible to grow food or even cover crops. This in turn acceleratessoil degradation and leads to desertification.

One of the few ways to reverse salination is to irrigate contaminatedsoils with clean water to wash-out the saline contaminants. This isoften not possible due to the lack of pure water. An alternative is toestablish salt tolerant species (e.g. pistachio, barley and sugar beet),then to minimise water use, and subsequently to ‘soak-up’ salts in theharvested crops. This is a gradual process which will allow a widerrange of less tolerant crops to be grown in the longer term.

Various proposals have been made for providing seed germination mediawhich provide the seeds with water, nutrients and protection during thegermination phase.

U.S. Pat. No. 5,189,833 discloses an arrangement in which lawn grassseeds are germinated in a thin layer of growing medium sprayed over amat of non-woven polypropylene lying on top of an impermeable membrane.After a few days of germination, the mat carrying the seed-bearingmedium can be lifted, rolled and then spread over an appropriatelyconditioned and prepared lawn bed. It will be appreciated that such anarrangement is neither intended nor suitable for growing crops inadverse environmental conditions.

Australian Patent Application AU-A-81394/75 discloses a seed bearing matcomprising upper and lower layers bonded together with a latex adhesive,seeds being bonded between the layers. The lower layer is a waterpermeable material such as straw, coconut fibres, peat moss or woodshavings whilst the upper or covering layer is formed from materials ofa finer texture than the lower layer such as coconut fibre dust orsawdust bonded together by latex. The seed bearing mat of AU-A-81394/75is described as being particularly useful in preparing lawns.

French Patent Application FR-A-2505607 discloses a non-laminar seedgermination medium comprising a folded layer of a transparent plasticsmaterial such as polyethylene having bonded to the edges of theunderside thereof a water-soluble or degradable seed-bearing medium suchas paper. In use, the seeds germinate beneath the transparent plasticslayer and, as the seedlings grow, they lift the transparent layer awayfrom the water-soluble/degradable medium. Thus the transparent layer isgradually unfolded and carried upwards by the growing seedlings andtherefore remains in place over the top of the plants to maintain agreenhouse effect.

French Patent Application FR-A-2440438 discloses a peat-based seedbearing medium comprising a lower layer formed of a water-permeablefibrous material such as cellulose fibres or muslin cloth, anintermediate layer of peat containing seeds and any additives; andoptionally an upper layer which is also water-permeable and can beformed from a material such as muslin. Although FR-A-2440438 disclosesthat the media are envisaged as being economical for large scale usesuch as plantations in and regions e.g deserts, it is also emphasisedthat an advantage of the peaty medium, compared with polyethylenesheets, is that it allows the penetration of rain water.

International Patent Application WO-A-96/28010 discloses a seedgermination medium in sheet form having upper and lower layers and seedsdisposed therebetween. The upper and lower layers are preferably formedfrom a biodegradable paper material. In order to assist anchoring of themedium in the underlying soil or, in the case of desert areas, sand, themedium is slit longitudinally to enable it to be stretched laterally toform an open lattice. However, it has been found that a problem with thelattice arrangement disclosed in WO-A-96/28010 is that it has a tendencyto dry out too quickly. In particular, when stretched to open out thelattice, the edges of the lattice openings lift exposing the lower layerof the medium and increasing water loss. Also, the lifting of the edgesof the lattice results in the seeds being lifted away from the soilwhich acts to inhibit germination of the seedlings, possibly throughbuild up of ethylene in the medium.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a seed germinationmedium which avoids the problems inherent in many known media and whichenables seeds to be germinated effectively in a range of different typesof environment, particularly arid and semi-arid areas and areas in whichsoil salination and desertification has taken hold. A further object ofthe invention is to provide a means of assisting germination anddevelopment of seedlings in land contaminated with organic and inorganicmaterials such as solvents and heavy metals.

Accordingly, in a first aspect, the invention provides aseed-germination medium comprising an upper layer formed from a tissuepaper having a weight of about 10 to 30 g/m², the tissue paper beingcoated or impregnated with a waterproofing agent such that the tissuepaper is permeable to gases but substantially impermeable to water inliquid form; a lower layer formed from a water-absorbent biodegradablematerial; seeds being disposed beneath the upper layer, and the upperlayer optionally having a plurality of perforations therein to assistdisruption of the upper layer to enable seedlings germinating from theseeds to grow therethrough.

Although the term “seed germination medium” is used above and in theclaims appended hereto, the terms “seed matrix” and “seed mat” are alsoused in the specification, and such terms are intended to be synonymouswith “seed germination medium” unless the context indicates otherwise.

The seed germination media of the invention are of a laminarconstruction, and typically comprise layers bonded together in such amanner that the layers cannot readily be separated without destroyingthem. In this respect, the media are distinguished from the mediadisclosed in FR-A-2505607 which are of a non-laminar arrangement inwhich the upper and lower sheets are connected only at their respectiveedges such that the upper sheet can be lifted away from the lower sheetby the action of the growing plant.

The upper layer optionally has a plurality of perforations therethroughthrough which seedlings may grow. Such perforations are preferred whenthe seedlings are of a more delicate or less robust nature and/or areinsufficiently strong to force their way through the upper layer.However, where the seedlings are of a more robust nature, and aresufficiently strong to burst through the upper layer, the perforationsmay be omitted.

The lower layer can also be provided with a plurality of perforations toenable roots emerging from the seeds to grow therethrough.

The coated or impregnated tissue paper from which the upper layer isformed should be partially permeable to water vapour but shouldnevertheless provide some barrier properties with respect to watervapour. A major function of the upper layer is to minimise loss of waterfrom the medium through evaporation, and to hold seeds in position whenexposed to wind, rain or harsh irrigation.

The term “tissue paper” paper as used herein refers to a lightweightmaterial with relatively poor mechanical strength typically having aweight of approximately 10 to 30 g/m², more usually 15 to 25 g/m², forexample from 17 g/m² to 24 g/m². The tissue paper typically hassufficient mechanical strength to enable it to remain intact duringmanufacture and laying but is preferably sufficiently weak when wet toallow stronger seedlings to grow through. For stronger grades of tissuepaper, for example papers at the upper ends of the weight ranges set outabove, perforations may be present in the upper layer to assist thegrowth of seedlings, particularly where the seedlings are ofinsufficient strength to burst or “punch” though the tissue.

The tissue paper can be calendered to give a polished surface and anexample of such a calendered paper is sulphite paper available fromKruger Tissue, Church Stretton, Shropshire, UK.

In order to provide the necessary waterproofing properties, the tissuepaper can be coated with a waterproofing material such as a wax or gaspermeable polymeric coatings In general, the coating of waterproofingagent is relatively thin, for example less than about 10 microns thick.The thin layer of waterproofing material is chosen so as to givewaterproofing properties for a short period of time until the seedlingestablishes itself, but contributes relatively little if at all to thestrength of the tissue. Examples of waterproofing polymers includebioerodible polymers and/or polymers which hydrolyse of otherwise breakdown slowly in the presence of water, air, ultraviolet light or heat, orunder the action of microbial attack In an alternative embodiment, thetissue paper can be impregnated with a waterproofing material, forexample a waterproofing adhesive (such as “Mystolene PS” available fromCatomance PLC, UK) which can consist of or contain a waterproofingpolymer as hereinbefore defined.

The upper and lower layers are typically bonded together by means of anadhesive. The adhesive is typically one which is non-phytotoxic, andmost preferably is water-based. Examples of such adhesives are starch,starch derivatives, polyvinyl alcohol (PVA) and ethylene vinyl acetate(EVA), optionally in combination with other adhesives. The adhesive canbe applied in such a manner and in such an amount that it permeates theupper layer thereby providing waterproofing properties to the upperlayer. Where the adhesive itself in of insufficient waterproofingcapability, a waterproofing agent can be added to the adhesive. Theadhesive is preferably one which is biodegradable or bioerodible.

The lower layer is an absorbent layer which can be made from a widerange of biodegradable materials including air-laid paper e.g. anair-laid latex bonded paper, for example a paper formed from fluff pulpand a latex binder; waste or recycled paper, or other fibre-based orwaste products. The selection of a suitable absorbent material for thelower layer will be dependent on cost, availability of raw materials andwater for irrigation; the soil type, irrigation method, degree ofcapillarity required and the amount of water which must be retained inthe medium to facilitate establishment of the seedling. In one preferredembodiment, 38-150 gm/m² air-laid paper is used to form the lower layer,one such form of material being available from Walkisoft of Steinfurt,Germany. Such air-laid papers typically contain approximately 85% fluffpulp and 15% latex binder, although greater or lesser amounts of bindercan be used as desired. Where availability of water is not a limitingfactor, the lower layer may be relatively non-absorbent, e.g. may beformed from newsprint or other recycled material.

The lower layer can be a single layer or it can comprise a plurality,e.g. two, three or four, of layers. As with the upper layer, the lowerlayer can be perforated to assist the penetration of roots emerging fromthe seeds, although with plants exhibiting strong root growth, this maybe unnecessary. The upper and/or lower layer can advantageously becoloured or treated to manipulate climatic conditions (e.g. to absorb orreflect heat) and to suppress weed growth below the medium. For example,the medium, or at least the surfaces thereof, can be provided in avariety of colours to assist soil warning/cooling or to exclude light soas to suppress weed growth and aid plant establishment. The medium mayhave different colours on its upper and lower surfaces to enhance orreduce the absorption of radiation on one surface and produce theopposite effect on its other surface.

In order to maximise weed suppression, the perforations in the upper andlower layers are preferably not in register, thereby ensuring that themedium cannot be expanded to form a lattice in the manner disclosed inWO-A-96/28010, and hence preventing weeds growing through. Theperforations can be slits or holes of any shape but, in the upper layer,preferably they are in the form of slits. The upper and lower layers canhave different numbers of perforations, and the perforations in therespective layers can be of the same general shape or a different shape.In general, the placement and size of the perforations and cuts will bedependent upon seed size, shape and type.

In addition to the seeds, a range of optional materials can be disposedbeneath the upper layer.

For example, fertilizers, micro-nutrients (such as zinc, copper, boron,and seaweed extracts), vitamins, humic acid, sea kelp, sugars, aminoacids, plant growth promoters and hormones, pH-regulators such as limeand sulphur, salt binding agents such as gypsum (calcium sulphate) andadsorbents such as activated carbon can be incorporated into the mediumeither by formulating with the adhesive or by application directly toone or other of the internal surfaces as a spray, granule or dust. ThepH-controlling agents can be used to control the acidity of theimmediate environment, and agents such as gypsum and activated charcoalcan minimise the impact of adverse chemical contaminants and salt in thesoil or medium, as well as to improve germination, and/or to aid andaccelerate plant establishment. Salt binding compounds, buffering and pHregulating compounds and adsorbents typically are applied at betweenabout 20 gsm and 200 gsm, more usually 50 to 150 gsm, for exampleapproximately 100 gsm. In the case of the adsorbent, activated carbon,lower concentrations are typically used.

The buffering and other chemical organic agents provide a means ofcounteracting the impact of adverse chemical contaminants in the soil ormedium, as well as improving germination, and/or aiding and acceleratingplant establishment. Thus, for example, lime provides a buffer againstlow pH, gypsum provides a means of counteracting high salinity, whereasclay minerals such as zeolite, kaolinite, calcium bentonite andmontmorillonite counteract high levels of fertiliser or chemicalcontamination in the soil.

Fertiliser and micronutrients may be added to the medium either byincorporation with the adhesive or applied directly to one or other ofthe internal surfaces as a spray, granule or dust. If applied at highlevels, fertilisers will produce a high level of EC(electro-conductivity) in the medium, which will scorch and killemerging seedlings. Consequently the rate of application, the type offertiliser used and the rate of release generally require carefulcontrol. Typically, organic based fertilisers are used since suchfertilisers release nitrogen more slowly allowing higher rates to beincluded in the medium without risk of damage to seedlings. A typicalapplication would be of a granular, organic-based material at between 10and 100 grammes per square meter (gsm), more typically 30-80 gsm.Fertilisers can vary considerably in their potassium, phosphorus andnitrogen contents, but one fertiliser useful in the media of theinvention contains 16% nitrogen, 10% phosphorous and 10% potassium plusmicro-nutrients.

Water retaining substances and wetting agents, which can be synthetic ornatural materials (such as clay minerals, e.g sodium bentonite (whichcan be applied at up to 100 gsm), or gelatine products, or surf such asnon-ionic, anionic, cationic and amphoteric surfactants or other wettingadjuvants), can be included to increase the water absorbency of themedium. Examples of such water-retaining substances include polymericgels such as polyoxyethylene gels (PEO), silica gels and so-called“super absorbents” such as super absorbent acrylic polymers (e.g.polyacrylamide), which may be added to the medium at between 5 and 100gsm, preferably 10 to 40 gsm, for example up to about 30 gsm dependingon use. Polyacrylamide is available for agricultural use from a range ofsuppliers including, for example, Glowcroft Ltd. Polyoxyethylene gels,which are particularly preferred in very hostile environments such ashighly saline soils, can be obtained from SmartTech Limited of Glasgow,UK, a particular PEO gel being cross-linked polyethylene oxideco-polyurethane hydrogel

In the case of wetting agents, these assist in dispersing the waterthroughout the medium, and allow less absorbent forms of paper or othersubstrate to be used.

Thus, an advantage of the seed germination media of the invention isthat they improve water utilisation. As such, they can be used to reducethe water requirement in situations (such as rice growing) whererelatively large amounts of water may normally be required either toenable germination to take place or to suppress weed growth.Furthermore, not only can the seed germination media of the inventionadvantageously be used to enable growth to take place in hostileterrains, but they can also be used in more temperate conditions, forexample in agriculture and horticulture, for example in growingsweetcorn, soya and salad crops.

Pesticides, (e.g. herbicides, fungicides, insecticides and nematicidesetc.) can be incorporated beneath the upper layer and preferably betweenthe layers. Although pesticide/micro-nutrient treated seed can be used,the pesticides can alternatively or additionally be incorporated into,or adsorbed or absorbed onto, the medium. This may reduce theconcentration of pesticide (and fertilizer) in direct contact with theseed allowing a broader range of products to be used at higher rateswithout causing phytotoxicity, reducing the requirement for fieldapplications and dose of active ingredient.

The seeds and optionally seeding agents such as propagation agents ofplant, animal and fungal origin can be bonded or held by physicalpressure at a predetermined density between the layers of the medium.The density of seeding will typically depend upon the required plantpopulation and environmental or field factors, for example. The seedscan advantageously be treated with pesticides of the type referred tohereinabove.

Where the lower layer is formed from a plurality of sheets, eachseparate layer can be impregnated with or carry a different additive.Thus, for example, an upper sheet can carry the seeds whilst plantnutrients can be carried by an underlying sheet.

Biological agents such as bacterial spores and fungal propagation agents(eg mycorrhizae) or other propagation agents may be used to encourageplant establishment in hostile environments and/or provide a means ofbiodegradation of the upper and lower layers. Bacteria and soil fungican buffer seedlings against soil contaminants (eg heavy metals) and maybe incorporated to attack the upper and/or lower layers to encouragebreakdown and the break through of seedlings. Typical biological agentsmay include any one or more of the following:

(a) vesicular arbuscular mycorrhiza fungi which will form symbioticassociations with the emerging roots and soil bacteria to encourageestablishment, especially in extreme conditions (eg Mycor manufacture byPlant Health Care Inc. or Symbio Limited of Great Bookham, UK);

(b) Pseudomonas spp. which are nitrogen fixing end which will encourageseed germination;

(c) Bacillus spp. To enhance seeding and encourage the development oforganic matter in the soil;

(d) Streptomycetaceas spp. or Trichoderma spp. to discourage thebuild-up of disease in the medium;

(e) other phosphorous solubilising and nitrogen fixing bacteria; and

(f) bacteria or fungi bred or selected to lock up, solubilise orinactivate a specific range soil contaminants such as hydrocarbons,toxic substances eg cyanide and heavy metals; and

(g) other microorganisms which degrade celluloses, starch and otherpolysaccharides.

Mixtures of bacterial plant growth activators that can be used in theseed germination media of the invention include commercially availableproducts such as “BioPak” (manufactured by Plant Health Care Inc) and“Organica” Plant Growth Activator (manufactured by Organica Ltd).

Depending upon the materials used, bonding of the upper and lower layerscan create a translaminar effect, which greatly enhances the movement ofwater across the medium from an irrigation source. The use of asemi-permeable layer on top reduces water loss from the absorbent layer,and super absorbents between layers reducing water demand.

The media of the invention can be provided with and/or used inconjunction with irrigation tubes. For example, one or more irrigationtubes can be sandwiched between the upper and lower layers or bonded toone or both of the exterior surfaces of the media. The irrigation tubescan be used together with solar pumps, for example, or heat sensitivemechanical pumps which control the distribution of water in accordancewith the requirements of the media in a given set of environmentalconditions. Irrigation tubes useful in the media of the invention caninclude trickle irrigation tubes which can be polymeric tubes havingperforations along their length, or tubes formed by folding sheets of apolymeric material such as polyethylene and tacking the edges togetherto form a leaky seam through which water can escape during use.

The medium of the invention can be provided with reinforcing means forincreasing its physical strength. The reinforcing means can be madesufficiently robust to enable the use of the medium as a groundanchoring medium in, for example, civil engineering applications, e.g.in the reinforcement of banks. In one embodiment, the reinforcing meanscan take the form of a mesh or netting made from a metal or plasticsmaterial, or can take the from of a fibrous reinforcement, such as afibrous mat.

Where reinforcing means are present, they are preferably secured to theupper surface of the medium, for example by means of adhesive bonding.By securing the reinforcing means to the upper surface, the medium isheld firmly in place. Moreover, irrigation tubes can be placed betweenthe reinforcing means and the medium, the reinforcing means holding theirrigation tubes in place for as long as is required, for example toenable long term maintenance. A particular application of such anarrangement is in the stabilization and maintenance of steep orotherwise unstable embankments such as road and rail embankments, ormining spoil or as a covering on waste disposal landfill sites.

In another aspect, the invention provides a process for stabilising anarea of ground (e.g. an embankment, such as a road or rail embankment,or mining spoilage or industrial or domestic waste dump, such as alandfill site) which comprises securing to the ground a seed germinationmedium as hereinbefore defined.

Either reinforced or non-reinforced medium can be used to stabilise anarea of ground but, in cases such as embankments (e.g. roadsideembankments) where the ground may be particularly unstable, thereinforced medium may be preferable.

In a still further aspect, the invention provides a method of growing aplant comprising placing a seed germination medium according to theinvention on or beneath a soil surface (for example a soil which issaline) and allowing or causing germination of seedlings from the seedsin the medium, such that the seedlings grow through the upper layer ofthe medium, for example by growing through perforations formed in theupper surface or by disrupting the upper surface to form a hole(s) andgrowing through the hole(s).

In a further aspect, the invention provides a process for making themedium as hereinbefore defined, the process comprising the steps of:

(i) providing a first web formed from a material which will constitutethe lower layer;

(ii) optionally forming a plurality of perforations in the first web;

(iii) depositing seeds onto the first web;

(iv) providing a second web formed from a material which will constitutethe upper layer,

(v) optionally forming a plurality of perforations in the second web,where such perforations are not already present;

(vi) optionally depositing adhesive on one or both of the first andsecond webs; and

(vi) bonding the first and second webs together.

Moisture from adhesives applied during manufacture may initially beabsorbed into the lower layer and any super absorbents present and suchabsorbed water may subsequently be imbibed by the seeds leading to adegree of pre-germination. As an alternative to encouragingpre-germination in this manner, seeds may be pre-treated beforemanufacture to pre-imbibe moisture by any one or more of a range oftechniques, including fermentation and chemical treatment. The advantageof pre-germinating the seeds is that it greatly reduces theestablishment time of the plant, and reduces the moisture requirementafter laying, without detriment to the seed. However, where the seedsare pre-germinated, care must be taken (e.g. by seed treatment ormoisture control) to avoid fungal and/or microbial attack on the seedsor physiological deterioration.

In a still further aspect, the invention provides apparatus formanufacturing a medium as hereinbefore defined, the apparatus comprisingfirst and second support means for holding respectively the first andsecond webs as hereinbefore defined; a bonding station for bonding thefirst and second webs together (e.g. by compressing the webs together);means for advancing the first and second webs towards the bondingstation; a seed dispenser upstream of the bonding station for depositingseeds onto the first web; optionally adhesive depositing means upstreamof the bonding station for applying adhesive to one or both of the webs;and optionally means for perforating one or both of the first and secondweb prior to or after bonding to form the medium.

The bonding station can take the form of a pair of rollers, the firstand second webs being conveyed through the nip between the rollers, forexample after adhesive has been applied to one or both of the webs, therollers exerting pressure on the webs to bring about bondingtherebetween. The rollers preferably are relatively soft, or at leasthave a resilient surface, so that the seeds are not damaged as the webspass between the rollers. Alternatively, bonding can be achieved byapplying tension to the finished roll of medium. The adhesive can bedeposited on the web(s) in the form of a spray (which can be for examplean electrostatic spray), or by means of a roller or brushes. Preferablyadhesive is deposited on the first web prior to depositing seeds on theweb so as to assist in retaining the seeds on the web as it istransported towards the bonding station. Adhesive is preferably alsodeposited on the second web upstream of the bonding station. Whenbonding is to be carried out by mechanical means rather than byadhesive, such mechanical means can be provided at the bonding station.

The formation of the perforations in each web can be effected by passingthe web over or through a cutter. The cutter can take the form of a pairof rollers, one having a plurality of cutting elements and the otherhaving a plurality of complimentary recesses for receiving the cuttingelements, the web being conveyed through the nip between the rollers.

In a preferred form of the invention, cutting of the webs takes place atthe bonding station, the bonding station comprising a roller or rollershaving laminating/compressing regions and cutting regions.

In a still further aspect, the invention provides a cutting and bondingroller for use in the apparatus of the invention, the cutting andbonding roller having one or more (preferably a plurality) axiallyspaced compression roller elements interspersed with one or more cuttingwheels. One or more spacer elements may optionally be disposed betweenadjacent compression roller elements.

In one embodiment, the cutting and bonding roller comprises a driveshaft having mounted thereon a plurality of compression rollers, one ormore cutter wheels being disposed between at least one pair of adjacentcompression rollers; and a plurality of spacer elements, the spacerelements being interposed between adjacent cutter wheels so as to spacethe cutter wheels apart. The drive shaft can have one or more slots orprotrusions or other keying means which cooperate with complimentaryformations on the cutter wheels and optionally the spacers so as to holdat least the cutter wheels against relative rotation with respect to thedrive shaft.

The cutter wheels have a plurality of cutting edges spaced (preferablyregularly) around their circumference. The cutting edges can be sawtoothed or arcuate in form, for example, and can be arranged in either acontinuous or discontinuous array. For example, in a discontinuousarray, the cutter wheel can have a plurality of cutting edges separatedby non-cutting edges of a smaller radius than the cutting edges, thecutting and non-cutting edges having substantially concentric radii. Ina continuous array, the cutting edges can have, for example, asubstantially sinusoidal form.

In another aspect, the invention provides an adhesive compositionsuitable for use in the matrices as hereinbefore defined, the adhesivecomprising a water soluble or water dispersible adhesive polymer such asPVA; and one or more (preferably two or more) agents selected frompesticides (for example herbicides, fungicides, insecticides,nematicides), plant micronutrients (such as zinc, copper, boron),organic and inorganic fertilisers, plant growth regulators (e.g. seaweedextract), plant growth promoters and hormones, buffering agents and pHregulators (e.g. lime and sulphur), and salt binding agents such asgypsum (calcium sulphate).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be illustrated, but not limited by reference tothe particular embodiments shown in the accompanying drawings of which:

FIG. 1 is a view from one side of a length of medium according to oneembodiment of the invention;

FIG. 2 is a sectional elevation along line I—I in FIG. 1;

FIG. 3 is a schematic partial cross sectional view illustrating the useof the medium;

FIG. 4 is a schematic side elevation of an apparatus for manufacturing amedium of the type shown in FIGS. 1 and 2;

FIG. 5a is a side view of a cutter roller of the type used in theapparatus of FIG. 4;

FIG. 5b illustrates schematically the arrangement of seed and additiveguiding baffles and their spatial relationship with the cutter roller ofFIG. 5a;

FIG. 6 is a schematic end view illustrating the medium of the inventioninstalled in a soil substrate; and

FIG. 7 is a schematic end view illustrating an alternative layout in asoil substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1 and 2, a medium 2 according to one embodimentof the invention comprises an upper layer 4 and a lower layer 6. Upperlayer 4 is formed from a lightweight tissue paper which in thisembodiment is a 22 grammes per square meter grade of sulphite paper(available from Kruger Tissue Group), which is permeable to gases, andpartially permeable to water vapour. The surface of the tissue paperlayer is treated with a coating of a wax during the manufacture of thegermination medium in order to render it impermeable to water in liquidform. Lower layer 6 is formed from a 38-150 gm/m² grade of air-laidpaper such as the 38 g air-laid paper available from Walkisoft GMBH,Steinfurt, Germany.

Disposed between the upper and lower layers 4,6 are seeds 8 which mayoptionally be coated (e.g. with one or more pesticides). Other desirableagents can also be disposed between the layers, examples beingsuper-absorbent substances for increasing the water carrying/retainingcapacity of the medium (such as “SwellGel”—available from Glowcroft Ltd,Gloucester, UK.), buffering agents, and beneficial bacteria and fungi asdescribed above.

The upper and lower layers 4,6 are bonded together by means of anadhesive layer 10 which, in this embodiment, comprises PVA. The PVA cancontain one or more agents such as pesticides (for example herbicides,fungicides, insecticides, nematicides), plant micronutrients (such aszinc, copper, boron), organic and inorganic fertilisers, plant growthregulators (e.g. seaweed extract), plant growth promoters and hormones,buffering agents and pH regulators (e.g. lime and sulphur), and saltbinding agents such as gypsum (calcium sulphate) and microbial speciesbeneficial to plant growth and development and/or which degradecellulose or other polysaccharides so as to bring about controlledbiodegradation of the two paper layers. The adhesive can be applied insuch a manner, and in such an amount, as to soak into the upper layer 4thereby providing the upper layer with at least temporary waterproofingproperties. In the event that the adhesive per se does not provide thedesired waterproofing properties, waterproofing additives such as beetleresin can be included in the adhesive. In the event that waterproofingis provided by the adhesive permeating into the upper layer, thewaterproof coating referred to above may be omitted.

Both the upper and lower layers 4,6 are perforated by an array of slits,the slits in the upper layer 4 being denoted by the number 12 in FIG. 1,and the slits in the lower layer 6 not being shown. The slits in theupper and lower layers 4,6 are not in register and therefore the mediumcannot be opened out into a lattice form in the manner of the mediumshown in WO 96/28010. The slits provide lines of weakness in the layerswhich enable the layers to be disrupted by the emerging seedlings sothat the seedlings can grow through. The slits in the lower layer 6 canbe omitted if desired.

An apparatus for manufacturing the medium of FIGS. 1 and 2 is shown inFIGS. 4 and 5. Thus the apparatus comprises a frame 20 to which arerotatably secured a spindle 22, upon which is mounted a roll 24 of theair-laid paper which will constitute the lower layer 6; and a spindleand roll core 26, upon which the finished medium is collected. Locatedbetween the spindles 22 and 26, in sequence, are an adhesive applicatorroller 28, guide rollers 29, a drum seeder station 30, a firstwaterproofing spray station 32, baffles 34, a bonding station 36comprising a pair of laminating rollers 38, a second waterproofing spraystation 40, and optionally a pair of cutter rollers 42 (which can beomitted if perforations are not required on the lower layer, or if thelaminating rollers at the bonding station at provided with cutters). Aseed dispensing hopper 56 and granule applicator 58 are mounted abovethe first web immediately upstream of the bonding station, and areconnected to the baffles 34 by means of chutes 60 and 62 respectively.Seed dispensing hopper 56 may be used as an alternative to the drumseeder station 30, or as an additional means of introducing seeds intothe medium.

Mounted above the product collecting spindle 26 is a spindle 46 uponwhich is mounted a roll 48 of the lightweight paper tissue which willconstitute the upper layer 4. Disposed between the spindle 46 and thelaminating rollers at the bonding station is an adhesive applicatorroller 50, guide rollers 51 and adhesive spray head 52 connected to asupply of aqueous adhesive (not shown).

In use, a web 100 of the air-laid paper is pulled through the machine bymeans of a powered drive shaft on the product collecting spindle 26. Theweb 100 is drawn along past the adhesive applicator roller 28, such thata thin film of adhesive is applied to the web and then passes under theseed drum 30 where seeds are deposited onto the web 100 from the drum.The web then moves along beneath the baffles 34 where granules of acomposition containing superabsorbent polymer, other desired additivessuch as buffers, and beneficial microbial species are dispensed fromgranule applicator 58. At this point, as an alternative (or addition) tousing the drum seeder 30, the seed dispensing hopper 56 may be used todeposit seeds onto the web. The baffles 34 serve to guide the granulesand seeds into longitudinal parallel rows.

At the bonding station 36, the web 102 forming the upper layer of themedium converges with the web 100, which has previously been coated withan adhesive by means of the adhesive roller applicators and the adhesivespray applicator. The two webs 100 and 102 are drawn between the rollers38 and compressed to bond them together. If plain rollers are used atthe bonding station 36, the two webs will be bonded together acrosstheir entire width. However, it is preferred that a roller of the typeshown in FIG. 5a is used in which case compression and bonding takesplace in lines spaced across the width of the webs. By configuring therollers 38, baffles 34 correctly, the seeds and other materials can beintroduced onto the web in rows such that compression and laminationtakes place either side of each row. This prevents any damage to theseeds as a result of the action of the rollers, and also ensures that amore secure bond is formed between the two webs at the locations wherethere are no seeds or other materials. The roller shown in FIG. 5a cutsslits into the medium at the same time as laminating the two webstogether, and thereby removes the need for a separate cutting orslitting station 40. However, as an alternative to using the rollershown in FIG. 5a, a roller having no cutting edges may be used, and aseparate cutting station 40 provided. After the bonding stage andsubsequent winding, some water from the adhesive may still remain in thepaper, held by the more absorbent lower web 100. Allowing the web toretain some water can lead to partial germination of the seed orinitiation of the germination step. This can be advantageous in certaincircumstances and, for example, can help to bring about more rapidestablishment of the plant when the medium is put to use. However, ifdesired, in order to reduce the water content of the glue, the webs mayoptionally be conveyed through an oven, drier or air-knife prior towinding onto the roll. Removal of the water prior to storage assists inmaintaining a prolonged shelf life for the medium.

The above process is preferably controlled by means of a centralprocessing unit 70 linked to the various motors used to drive thespindles, compression rollers and seed, adhesive and additive dispensingmeans thereby ensuring greater consistency in the end product.

The size of the rolls of seed germination medium formed according to theforegoing process will depend upon the raw materials, the intendedmethod of laying (by agricultural machinery or by hand), and the areaintended to be covered. However, purely by way of example, the rolls canbe up to 1.2 meters wide, 4200 meters in length, and may cover up toabout 0.5 hectares or more.

It will be appreciated that various modifications can be made to theprocess described above. For example, in the process described above,the upper and optionally the lower webs are slit by cutter rollers.However, instead of cutting the slits during the process, one or both ofthe webs can be pre-cut. In certain instances, the lower layer 6 of themedium need not be cut at all, the rooting strength of the germinatingseedling being sufficient to force a way through the lower surface ofthe medium.

Also, the Figures illustrate the germination medium being manufacturedwith the lower layer 6 of the medium being formed by the lower web 100,and the upper layer 4 by the upper web 102. However, the apparatusillustrated, and in particular the positioning of the adhesive rollersand sprays, and the waterproofing spray heads, is sufficiently versatilethat it could equally be set up in the reverse configuration should theneed arise.

In order to effect accurate placement of the seeds, the seeds canapplied using the drum seeder 30. However, as an alternative, the seedhopper/plate seeder 56 or a similar device could be used to broadcastseed on to the web. Other biological agents such as bacterial spores maybe added in the same way. As indicated above, the seeds can be laid intorows using the baffles as guides, but they need not be, but insteadcould be spread evenly over the entire surface of the web.

A typical laminating and cutting roller used in the apparatus of theinvention is shown in FIG. 5a Each cutter roller comprises a centralspindle or drive shaft 200 on which is mounted an array of compressionrollers (d), narrow spacers (c) cutter wheels (a) and wide spacers (b).The compression rollers, cutter wheels and spacers are held againstrotation on the spindle by means of key slots (not shown) which engage aspline (not shown) on the spindle. As can be seen from the Figure, eachpair of adjacent compression rollers (d) has a pair of cutter wheels (a)arranged therebetween, the cutter wheels (a) being spaced from eachother by means of a large spacer (b) and from the compression rollers(d) by means of narrow spacers (c).

In FIG. 5b, the alignment of the baffles with regard to the variouselements of the bonding rollers is shown. Thus, the gaps between thebaffles are aligned with the wide spacers (b) such that seeds and othermaterials are deposited onto the web between the regions of the websthat are subjected to compression by the compression rollers (d). Bypositioning the cutter wheels (a) such that they are at the edges of theunbonded regions of the medium, lines of weakness are formed that enablethe developing seedlings more easily to rupture and grow through theupper layer.

The seed germination medium of the invention can be laid using existingagricultural or horticultural equipment, for example the machinerytypically used for laying polyethylene sheeting, or crop mulchingequipment In general, the soil or ground can be prepared in advance ofthe laying to produce a relatively smooth clod free bed. Furrows F arethen opened up on either side of the medium and the medium is partiallyburied as shown in FIG. 6 and 7. Burying the edges E of the medium helpsto hold it in place against the action of, for example, winds. Trickleirrigation tubes T (for example of the “Drip Tape” type—available fromWright Rain Limited, Ringwood, UK) can be incorporated at laying or themedium may be wetted utilizing overhead, ditch or flood irrigation. Asmuch of the medium as possible should be covered to assist establishmentand reduce water consumption although the medium can be laid on thesurface if necessary and an appropriate securing system used. Oncewetted, the medium will retain moisture to allow the seeds to germinate.Ideally little or no further moisture should be applied to encouragerapid deep rooting and self sustainability. However, this may not bepractical in all situations and additional water may be required. As analternative to trickle irrigation, a form of flood irrigation could beused by laying the medium into a depression in the ground, which mayformed manually or by the equipment used to lay the medium, and allowingor causing water to run over the surface of the upper layer.

The advantage of the medium of the present invention is that it providesa protected local environment which is favourable to the germination ofseeds and the subsequent development of seedlings. The medium has asubstantially reduced water demand compared to conventional overhead andtrickle irrigation systems, and can be applied to land using existingplastic/mulch laying equipment. A further benefit of the medium is itscompatibility with existing trickle, overhead, trench and floodirrigation systems. Once the medium has been laid, there is a minimalrequirement for additional irrigation. If desired, however, a trickleirrigation system can be incorporated into the medium at manufacture.Further substantial advantages are the ease of manufacture of the mediumand its long shelf life. Moreover, the medium can be used in bothhostile and normal agricultural situations.

EXAMPLE

The following examples illustrate the properties of various seedgermination media prepared in the manner described above.

Example 1 Effect on Seedling Growth of Various Additives

A number of samples were made up using 50 gsm (grammes per square meterweight) air-laid paper for the lower layer and sulphited tissue paper asthe upper layer. The materials were cut to 10 cm² squares beforeapplying seeds and various additives and then laminating. A starch-basedadhesive incorporating a waterproofing agent (obtained from NationalStarch NS Ref. 0720185) was used to laminate the two layers together.Various additives were placed in two discrete rows 2 cm wide with a 1 cmgap between rows and at the edges on to the lower absorbent layer.Adhesive was applied to the upper layer which was then laminated to thelower layer using a profiled roller of the type shown in FIG. 5a.Samples were labelled and placed into 10 cm² petri dishes over a fixedquantity of vermiculite with 10 ml of water. Samples were left underglass. Seedling germination, vigour and penetration of the upper lagerwere observed and recorded. The quantities of additives incorporatedinto the various samples are shown in Table 1 below, and the effects ofthe additives on seedling growth are shown in Table 2.

TABLE 1 Samples and Application Rates (gsm) Application Rates (gsm)Fertiliser Rate (gsm) 0 10 20 30 F0 Fertiliser (F) @ 0, 0 0.1 0.2 0.3F10 10, 20, 30 gsm F20 F30 P5, F0 F + Plant growth 0.05 0.15 0.25 0.35P5, F10 stimulator (PGS) @ P5, F20 5 gsm P5, F30 L100, F0 F + lime (L) @1.0 1.1 1.2 1.3 L100, F10 100 gsm L100, F20 L100, F30 G30, F0 F +polyacrylamide 0.3 0.4 0.5 0.6 G30, F10 gel (PAG) @ 30 gsm G30, F20 G30,F30 P5, G30, F0 F + PGS + PAG 0.35 0.75 P5, G30, F20 P5, G30, L100, F0F + PGS + PAG + L 1.35 2.15 P5, G30, L100, F20 P5, G15, f20, L100 F +PGS + PAG + L 1.35 P5, G15, F20, L0 F + PGS + PAG 0.4 Key F = Fertiliser(14:10:27 with some trace elements) P = Plant growth stimulants -proprietary brand manufactured by Organica Ltd L = Lime G =Super-absorbent gel (polyacrylamide)

TABLE 2 Vigour 0 = dead, Sample 5 = strong Notes F0 2 Germination andpenetration OK but weaker than others after 2 weeks. F10 3 Good growthand establishment. F20 4 Good growth and establishment. F30 5 Verystrong. P5, F0 4 Quick to establish. Upper and lower layer destroyed bybacteria on all samples. P5, F10 4 Slow to establish. Some evidence ofanaerobic conditions. P5, F20 2 Slow to establish. P5, F30 1 Poor -probably kept too wet so bacteria took hold: rate too high? L100, F0 3Weak but OK. L100, F10 3 Weak but OK. L100, F20 3 Weak but OK. L100, F305 Very strong. G30, F0 5 Very strong and lifting upper layer throughoutbatches. Rate too high. G30, F10 5 G30, F20 5 G30, F30 5 P5, G30, F0 5Very strong. Lifting upper layer. P5, G30, F20 5 P5, G30, L100, F0 5Very strong. Lifting upper layer. P5, G30, L100, F20 5 P5, G15, f20,L100 5 Very strong. Lifting upper layer. P5, G15, F20, L0 5

Conclusions

The data demonstrate that:

(a) the bacteria present in the plant growth stimulator have abeneficial effect on the establishment of the seedlings and that,moreover, they cause beneficial rotting of the upper and lower layers.However, damage to the seedlings can result if the conditions are kepttoo wet. The concentration (rate) of application of the PGS is probablytoo high and preferably should be lowered to about 1 gsm;

(b) lime was found to have no negative or positive interaction withother materials in the trial;

(c) fertiliser was found not to suppress growth at up to 30 gsm, andtherefore higher rates could be tried;

(d) too much polyacrylamide gel separates the layers and allowsseedlings to establish between the layers rather than encouragingseedling penetration. Therefore, the concentration of PAG should bereduced.

On the basis of the test data obtained to date, one preferredcomposition for use in the seed germination media of the invention is asfollows:

Polyacrylamide 10 gsm Fertiliser 20 gsm Bacteria (plant growthstimulator)  1 gsm Lime 54 gsm Fine grade vermiculite  5 gsm

The purpose of the fine grade vermiculite is to improve aeration andreduce the risk of anaerobic conditions developing in the medium.

Example 2 Germination of Grass Species in Saline Soils

Experiments were conducted in order to evaluate a seed germinationmatrix of the invention as a means of promoting the germination,subsequent emergence and growth of eight grass species in saline soils.A saline soil is that which has an electrical conductivity of greaterthan 4 dS/m. Experiments were also carried out to evaluate theinteraction of various microbiological additives with the grass species.

Materials and Methods

Preparation of the Saline Growing Substrates

The following salts (calcium chloride, magnesium chloride and sodiumchloride) were applied to a sterilised growing substrate (John InnesSeed Compost) at rates which were sufficient to increase the electricalconductivity to 12 dS/m (medium salinity) and 22 dS/m (high salinity)following the method of Rowell (Soil Science, Methods and Applications,Publ. Longman Scientific & Technical, 1994). The untreated substrate wasused as the control and had an electrical conductivity of 2.5 dS/m. Themeasurement of electrical conductivity was performed as follows: 20grammes of soil and 100 ml of substrate were shaken for one hour afterwhich the suspensions were allowed to settle and the electricalconductivity of the supernatants was measured using either a DiST 3, orDiST 4 handheld conductivity meter. These values were converted to thoserepresentative of the saturated extract, following the method of Rowell(1994). The substrates and salts (where required) were mixed togetherusing a compost mixer to ensure an even distribution of salts throughoutthe substrate.

Selection of Grass Species.

Following consultation with established seed merchants (Pope andChapman, Bishops Stortford, UK) and the technical literature, eightgrass species, of varying tolerances to salinity, were selected. Theseincluded amenity and agricultural cultivars and are listed in Table 3.Germination tests, using a standard technique, were conducted at 25degrees Celsius and these showed that at least 85% of each seed speciesgerminated within 14 days from the start of the test.

TABLE 3 Grass species listed in order of tolerance to saline conditionsSeed rate Species Cultivar (g/sq. m) Saltmarsh Grass Pucinella distansSalty 40 Slender Red Fescue Festuca rubra litoralis Smirna 40 Dwarf TallFescue Festuca arundinaceae Cochise 30 Creeping Bent Agrostisstolonifera Kromi 10 Fine Perennial Ryegrass (PRg) Lolium perenne Numan25 Strong Creeping Red Fescue Festuca rubra rubra Pernille 40 TetraploidAgricultural. PRg Lolium perenne Calibra 30 Smooth Stalk Meadow GrassPoa pratensis Conni 20

Microbiological Additives

A range of soil bacterial and fungal inoculants were incorporated intothe matrix for evaluation. A proprietary mix of inoculants (Symbio Ltd,Great Bookham, UK) was selected for the trial. The mix includedvesicular-arbuscular mycorrhizae, pseudomonas, and bacillus species anda range of other phosphorous solubilising and nitrogen fixing bacteriawith biostimulants. In this example, for simplicity, the fungi, bacteriaand additives used are generally referred to as ‘bugs’.

Manufacture of the Matrix

Samples (0.15 sq.m) were made by hand from a super-absorbent air-laidpaper (Walkisoft) forming a lower layer and perforated sulphite paper(Kruger Tissue, Church Stretton, Shropshire, UK) forming the upperlayer. An aluminium frame was used to subdivide the lower layer into 16strips, each 30 cm in length, and 2 rows were allocated to eachcultivar. Seeds, fertilisers (Westland Specialist Feed-All),polyacrylamide gel (“Swell Gel”—Glowcroft Limited)) were applied to alltreatments and the microbiological additives were applied at theequivalent field rate to half of the treatments. The application rateswere as follows: fertiliser (20 g/sq.m), polyacrylamide gel (30 g/sq.m)and the microbiological additives at 50 g/sq.m.

A PVA adhesive (Mystolene, Colomance PLC, Welwyn Garden City, UK) wasapplied to the upper layer which was then bonded to the lower layerusing a laminating process which bound the layers and encapsulated theseed and additives. A wax emulsion was sprayed onto the exposed surfaceof the upper layer to provide waterproofing.

Preparation of the Containers and Laving of the Matrix

“Sankey” trays (0.58 m*0.38 m) were used to contain each treatmentHorticultural grade coarse grit (nominal size 4mm) was poured into thebase of each tray (3.5 liters per tray), after which 2 liters of mainswater was added. The gravel served two purposes: firstly, to prevent thesubstrate slumping into the base of the trays and, secondly, to act as areservoir. The substrate (8 liters) was then placed over thewater-filled gravel, the matrix was laid over the substrate, and half ofthe matrix was buried.

Trays were also directly sown without the matrix, using the samecultivars to assess the benefits of the matrix. In this case only theseeds were applied. The quantities of gravel, water and substrate werethe same as described above.

Treatments and Trial Design

The treatments are summarised in Table 4. There were three trays foreach treatment and one for each control. All the trays were placed in aheated and lit greenhouse. The average daily temperature was 20° C. andthe lights were on for a period of 12 hours each day(08:00-20:00).providing a light intensity of 61 micro mols/sq.m/second.

TABLE 4 Summary of treatments Low salinity Medium Salinity High salinity(2.5 dS/m) (8 dS/m) (13 dS/m) Treatments + bugs + bugs + bugs − bugs −bugs − bugs Control seed only seed only seed only

Additional water was applied after 14 days and, for the remainder of thetrial, in response to use. The water content of the trays was maintainedbelow field capacity (where the substrate would slump leading tophysiological stress).

Sampling

After 28 days the grasses were harvested from the buried side. A grid(0.0015 sq.m) was placed over both ends of the rows and the grassenclosed therein was cut at the soil surface/matrix surface. The grasssamples were placed in pre-weighed paper bags and together were dried at80° C. for 24 hours after which they were weighed again to determine thedry matter percentage of each sample. In addition, the numbers of plantsand leaves were determined for one of the species, the tetraploidagricultural perennial ryegrass (c.v. Calibra). The mean dry matterproduction per square meter of the various cultivars are summarised inTable 5 below.

TABLE 5 Matrix Matrix Matrix Matrix Matrix Matrix Mean dry matter (gControl Low Low Control Medium Medium Control High High per sq.m Low NoBugs Bugs Medium No Bugs Bugs High No Bugs Bugs Salty 47 44 64 10 38 170 7 34 Smirna 52 89 75 0 46 30 0 4 3 Cochise 82 144 96 0 78 74 0 25 37Kromi 70 52 33 0 55 32 0 0 0 Newman 73 178 172 31 111 96 0 11 37Pernille 45 54 70 0 45 60 0 0 9 Calibra 66 241 211 26 108 139 0 25 25Conni 20 35 48 0 17 12 0 0 0

Observations

All of the varieties tested responded well in medium salinity soil andfour responded well in high salinity soil. Thus, after 7 days the Numanand Calibra varieties had emerged from the low and medium salinitytreatments. The emerged seedlings came from that part of the matrixwhich was buried. In the low salinity control tray Numan, Calibra, Kromiand Pernille had emerged and in the medium salinity tray only Numan hademerged.

After 14 days all of the cultivars had emerged from the low and mediumsalinity treatments and the corresponding controls. Emergence was muchreduced and slower from the high salinity treatments and thecorresponding control tray. During this time, salt deposits wereobserved on the soil and matrix surfaces in the medium and high salinitytreatments including control plots.

Subsequently there was only limited germination and emergence from thematrix that was uncovered and had been laid on the surface of thesubstrate, especially where there was poor contact between the uncoveredmatrix and the underlying substrate. Consequently, no comparative datawere taken from this area.

After harvest the matrix was removed from each tray. It was clear thatnot only had germination failed where the matrix was not buried but thatsubstantial quantities of salt had been deposited between the matrix andthe substrate surface, in addition to the salts which were deposited onthe uncovered matrix surface.

It seems likely that the salt deposition problem was caused by a“wicking” action whereby water containing salts is drawn up through thematrix by the superabsorbent polyacrylamide gel as the upper surface ofthe matrix dries out in air. This phenomenon did not give rise to anyappreciable problems with germination when the matrix was buried. Afurther advantage of burying the matrix was that those parts of thematrix that were buried in the low and medium salinity treatments hadmostly decomposed after 28 days.

Four cultivars demonstrated considerable potential for subsequenttrials: Cochise and Pernille (fescue spp.) and Numan and Calibra(ryegrass spp.). However, Pernille was situated between the twoaggressive ryegrass cultivars which may have out competed the fescue.The mean dry matter productions per square meter of the followingcultivars; Cochise, Newman, Pernille and Calibra, are summarised inTable 6.

TABLE 6 Dry matter production per square meter. Cochise Numan PernilleCalibra Low Salinity Control 82 73 45 66 Matrix + bugs 96 172 70 211Matrix − bugs 144 178 54 241 Medium Salinity Control 0 31 0 26 Matrix +bugs 74 96 60 139 Matrix − bugs 78 111 45 108 High Salinity Control 0 00 0 Matrix + bugs 37 37 9 25 Matrix − bugs 25 11 0 25

The greatest increase was observed within the low salinity treatmentswhere the matrix gave a clear advantage over the direct sown treatment.There was an apparent reduction in yield where the “bugs” were appliedto the matrix. The medium treatments followed a similar pattern; Thelargest yield difference occurring between the matrix treatments and thecontrol. In contrast to the low treatments, Calibra produced largeryield of dry matter when “bugs” were incorporated into the matrix.Pernille produced larger yields of dry matter In both low and mediumlevels of salinity in response to the +“bugs” treatments. Both Cochiseand Numan apparently provided larger yields where no “bugs” wereincorporated within the matrix.

Data from the high salinity treatments showed that plant growth wassuppressed where the seeds were sown directly into the saline soil. BothCochise and Numan produced larger yields of dry matter from the +“bugs”treatment, whereas the yields of Calibra were the same in bothtreatments.

The results of the experiments demonstrated that the matrices of theinvention promote the establishment and growth of seedlings in salineconditions where otherwise grass species will not grow. Themicrobiological additives provided apparent benefits with some grassspecies but not with others. Complete burial of the matrix ensured evengermination and emergence in saline conditions but the results showedthat alternative absorbents of buffering agents are required for surfaceuse on saline soils, since the polyacrylamide gels concentrate salts atthe surface in highly saline soils.

Example 3 Experiments Illustrating the use of Germination MatricesContaining PEO Buffering Agents in Saline Soils

Further experiments were carried out to test the effectiveness of thematrices of the invention in enhancing the establishment of grass andclover in saline and hostile environments. The tests were carried out inNSW, Australia. In particular, the experiments were designed todetermine the most appropriate buffering materials, absorbents andmicrobiological agents for use in saline soils.

Soil salinity is a major and increasing limitation to agriculturalproduction. It is caused by the accumulation of salts in the rootingzone. At higher levels (above 6 dS/m) the presence of salt affects manycrops and prevents all but tolerant species from being established. Oneway to overcome this problem is to leach the salts out of the soilprofile. Continual irrigation will prevent salts being drawn back to thesurface but if insufficient water is applied salinity will increase assalts are drawn up to the surface. Without effective management thesesoils may be lost from agricultural production thereby beginning theprocess of desertification.

High levels of salinity in the rooting zone inhibit plant establishmentin three ways:

1. Physiological drought caused by a reduction in the availability ofwater to plants by lowering the osmotic potential, despite the apparentavailability of water.

2. Toxicity effects of sodium and chloride and ionic imbalance in theplant

3. Structural deterioration leading to capping of the topsoil.

Plant growth at the saline trial site was impaired by a combination ofthese factors.

The matrix of the invention incorporates various buffers and absorbentsto allow plants to be established in hostile conditions with minimumwater requirement. Microbiological additives (bacteria and mycorrhizae)may also be included in the seed mat. Plant growth is enhanced incertain environments where plant roots have been inoculated with theseorganisms and inoculation is more successful where seeds, bacteria andmycorrhizae are placed together in a protective environment

In this series of experiments, field plots were established at FreemansReach, near Hawkesbury, NSW, Australia. The plots were selected on thebasis that they had saline soils that were a major problem to thefarmer. The majority of soils at Freemans Reach are clay loams overlyingclay that is mottled, a characteristic of poorly drained soils. Thetopsoil has a weak structure that sets hard when dry. The soils have abackground salinity of at least 8 dS/m. Soil salinity has developedthrough effluent seepage from a nearby intensive livestock units andfrom groundwater which is inherently saline. The former has also led toexcessive levels of phosphorous in the soils within the catchment andconsequently an antagonistic reaction to some of the soil bacteria wasexpected.

The effect of soil salinity on the growth of indigenous grass and cloverspecies was investigated using the seed germination mats of theinvention and (for comparison and control purposes) direct sown plots.The experiments were undertaken in two distinct stages. In the firststage, seed mats were produced that contained a variety of species(Table 7) with a range of buffering and bacterial inoculants in variouscombinations (Tables 8 & 9). These were laid and subjective observationswere made to determine the most appropriate range of additives. Theresults were subsequently incorporated into larger 10 meter plots.Results from the more extensive study were quantitatively assessed usingdry matter production and these are presented below (Table 10).

Materials and Methods

Seven grasses and one clover cultivar (Table 1) were selected asindicator species, as follows:

TABLE 7 Grass and clover species Application rate Species (kg/ha) Tallwheat grass (Agropyron elongatum) 200 Creeping red fescue (Festucarubra) 200 Finelawn petite dwarf fescue (Festuca arundinacea) 200 Gatorryegrass (Lolium perenne) 200 Tetila ryegrass (Lolium perenne) 25Kentucky bluegrass (Poa pretensis) 50 Palestine strawberry clover(Trifolium fragiferum) 5 Penncross hybrid bent (Agrostis stolonifera)100

Species were individually segregated in the first observation andsubsequently mixed for the larger plots.

A range of additives including buffering agents, water absorbents(synthetic products and clay minerals) and bacterial inoculants wereincluded in the initial assessments (Table 8,9).

TABLE 8 Additives Additive Application rate (kg/ha) Calcium bentonite 25g/m² (clay mineral from the montmorillonite group) Zeolite 15 g/m² (claymineral from the montmorillonite group) Polyacrylamide (Pa) 25 g/m²(marketed as ‘Swellgel Rootdip’) PEO Hydrogel* 50 g/m² A-100 15 g/m²(bacterial inoculant supplied by Ambello Pty *A buffer/absorbent foundfrom polyoxyethylene and available from Smart-Tec Ltd, Edinburgh, UK)

In the initial plot work, grasses and clover species were kept separateand each species was laid in two adjacent rows, 30 cm apart, ontoair-laid paper. Additives were applied evenly over the seeded area, withthe exception of A-100, a bacterial inoculant, that was applied atlogarithmic scale in order to assess its effect on seed germination andto determine a suitable rate of application. Perforated and calenderedtissue paper was then attached, using PVA adhesive, and laminated toproduce a seed mat.

Before laying, the sites were surveyed to determine the level ofsalinity by measuring the electrical conductivity (ECe). Salinity wastypically 8 dS/m with one small area at 3.2 dS/m. The area with lowsalinity was at the top of the gentle slope where increased leaching ofthe salts was possible. Consequently this was included in the study as acontrol area. A lower lying area was selected for undertaking the bulkof the trials where higher levels were consistent.

TABLE 9 Treatments and combinations of additives. Treat- Seed A-100 PEOCalcium- ment Seed mat (Bacteria) Pa Hydrogel Bentonite Zeolite A ✓ B ✓✓ C ✓ ✓ ✓ E ✓ ✓ ✓ F ✓ ✓ ✓ ✓ G ✓ ✓ ✓ H ✓ ✓ ✓ ✓ ✓ I ✓ ✓ ✓ ✓ J ✓ ✓ ✓ ✓ L ✓✓ ✓ ✓ N ✓ ✓ ✓ ✓ ✓ P ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ R ✓ ✓ ✓ ✓ ✓ ✓ S ✓ ✓ ✓ ✓ ✓ ✓

The pre-prepared sample rolls were laid onto the top of raised beds onMar. 9, 2000 with direct seeded controls in the high and low salineareas of the site. The top of the bed was levelled and soil was moved tothe outer edge. The mats were laid on the levelled surface and soil wasdrawn onto the mat to provide a covering of between 10 and 20 mm. Thecontrol treatments were direct sown on the beds at the end of the seedmat treatments. Seeds were sown into rows; these were then covered withthe same depth of soil to mimic the treatment plots as closely aspossible. Irrigation of the plots was unnecessary as the area sufferedfrom unprecedented levels of rainfall following laying. This resulted instructural damage of the topsoil and subsequent capping. Poor aerationensued which provided a very hostile environment.

Observations From Preliminary Plots

Emergence was delayed until the soil surface dried; capping of the soilsurface inhibited emergence of some species, especially in controlplots. In spite of these conditions, the most prominent growth wasobserved from the parts of the mat containing PEO Hydrogel, calciumbentonite and zeolite. Very little growth occurred without the use ofthe seed mat of the invention It was not possible to ascertain whetherthere was any effect from the use of the bacterial inoculant, A-100.

Preparation of Seed Mats for Larger Scale Assessments

Seed mats were prepared on the basis of the above observations with PEOHydrogel, calcium bentonite, zeolite and with and without the inclusionof A-100 bacterial inoculant, applied evenly at 15 g/sq.m. Grass andclover species were mixed before application in rows. Otherwise themanufacturing protocol remained unchanged.

Laying

Strips of the seed mat of the invention were laid on Mar. 17, 2000 andwere covered with 10 mm soil. Soil conditions were too wet to attempt todirect seed control plots at the same time. Consequently results weretaken from previously seeded areas as part of the initial study.

Results

Emergence of ryegrass species was observed by Mar, 23 (7 days afterlaying) despite 81 mm rainfall during the intervening period.Assessments were made 20 days after emergence. Plant material washarvested using quadrats (0.25 m×0.25 m). A total of 10 sub samples weretaken from each mat. Fresh weights were recorded at the time of samplingand the plant material was then dried at 80° C. for 24 hours. Total drymatter production was assessed 20 days after emergence on April. 14Results are summarised in Table 10 and shown in detail at Table 11

There was limited, if any, growth of grasses in the saline control plotsafter 20 days after emergence of the seed mat Ned plots so no it was notpossible to harvest and record from the sub-plots.

TABLE 10 Summary of results from 10 m plots Salinity Dry matter SiteTreatment dS/m g/m² Farm site Seed mat − >6 32 (± 3.1) (Laid Mar. 17,2000) bacteria Farm site Seed mat + >6 19 (± 2.1) (Laid Mar. 17, 2000)bacteria Farm site Direct seeded <2 <1 (Sown Jul. 3, 2000) Farm siteDirect seeded >6 <1 Sown Jul. 3, 2000)

In spite of the additional rain following the laying of the matrix (seedmat), growth in the 10 m plots was far better than the direct sown areaswith an equivalent level of soil salinity. In one area of the farm sitethat was higher up a slope, high rainfall had leached the salinity tobelow 2 dS/m. In this one area, direct seeded treatments had establishedbut in all other control areas no emergence occurred.

TABLE 5 Dry matter production Rep no. Fresh wt (g) g/sq. m Dry wt (g) gDM/sq. m DM (%) Freemans Reach + bacteria 1 6.4 102.4 0.6 9.6 9.4 2 8.3132.8 1.0 16.0 12.0 3 5.7 91.2 0.5 8.0 8.8 4 12.2 195.2 1.1 17.6 9.0 513.2 211.2 1.3 20.8 9.8 6 14.6 233.6 1.2 19.2 8.2 7 16.3 260.8 1.5 24.09.2 8 16.0 256.0 1.4 22.4 8.8 9 20.3 324.8 1.9 30.4 9.4 10  15.7 251.21.5 24.0 9.6 Mean 13 206 1 19 9 Std. Dev 4.7 75.9 0.4 6.8 1.0 Std. Error1.5 24.0 0.1 2.1 0.3 Freemans Reach − bacteria 1 33.3 532.8 2.9 46.4 8.72 26.5 424.0 2.6 41.6 9.8 3 21.5 344.0 2.0 32.0 9.3 4 22.1 353.6 2.032.0 9.0 5 24.0 384.0 2.2 35.2 9.2 6 26.4 422.4 2.4 38.4 9.1 7 13.3212.8 1.1 17.6 8.3 8 25.4 406.4 2.2 35.2 8.7 9 14.6 233.6 1.8 28.8 12.310  10.6 169.6 0.9 14.4 8.5 Mean 22 348 2 32 9 Std. Dev 7.0 112.3 0.69.9 1.2 Std. Error 2.2 35.5 0.2 3.1 0.4

Conclusions

The results demonstrated that the use of the seed matrices (seed mats)of the invention without additives gives a degree of physical protectionthroughout, but germination is much more effective when a combination ofPEO Hydrogel, calcium bentonite and zeolite are included in the mat.

The results also demonstrate that the polyacrylamide gel superabsorbentwas relatively ineffective in the saline conditions encountered in thisstudy. This is believed to be the result of phytotoxicity and, possibly,the creation of an anaerobic microclimate within the mat once the gelformed. There is also the risk of salt accumulation within the gel,which in turn will inhibit seed germination.

Burying of the matrix has no detrimental effect on germination andprotected emerging seedlings from the effect of heavy rainfall.

The inclusion of the A-100 bacterial inoculant gave no discernibleadvantage.

Weed control was substantially increased where the seed mat of theinvention was laid in comparison to direct seeding.

The foregoing Examples illustrate the advantages of the seed matrices(seed mats) of the invention in both low salinity soils and also highersalinity more hostile conditions.

It will readily be apparent that numerous alternations and modificationscould be made to the medium shown in the accompanying drawings anddescribed in the Examples without departing from the principlesunderlying the invention and all such modifications and alterations areintended to be within the scope of this application.

What is claimed is:
 1. A seed germination medium comprising an upperlayer which is permeable to gases but substantially impermeable to waterin liquid form; a lower layer formed from a water absorbentbiodegradable material; and seeds being disposed beneath the upperlayer, wherein said upper layer having a plurality of perforationstherein to assist disruption of the upper layer to enable seedlingsgerminating from the seeds to grow therethrough.
 2. The seed germinationmedium of claim 1, wherein said upper layer is composed of a tissuepaper having a weight of approximately 10-30 g/m² and being coated orimpregnated with a waterproofing agent such that the tissue paper ispermeable to gases but substantially impermeable to water in liquidform.
 3. A seed germination medium according to claim 2 wherein thetissue paper is a lightweight material having a weight of from 15 to 25g/m² for example from 17 g/m² to 24 g/m².
 4. A seed germination mediumaccording to claim 2 wherein the tissue paper is a calendered paper. 5.A seed germination medium according to claim 2 wherein the tissue paperis a sulphite paper.
 6. A seed germination medium according to claim 2wherein a water-absorbent substance is disposed between the upper andlower layers.
 7. A seed germination medium according to claim 6 whereinthe water-absorbent substance is a polyoxethylene gel, for example across-linked gel such as a cross-linked polyethylene oxideco-polyurethane hydrogel.
 8. A seed germination medium according toclaim 2 wherein the tissue paper is coated with a waterproofingmaterial.
 9. A seed germination medium according to claim 8 wherein thewaterproofing material is a waxy substance.
 10. A seed germinationmedium according to claim 8 wherein the waterproofing material is apolymer which is subject to degradation or erosion under the influenceof water, ultraviolet radiation, heat, aerial oxidation, or microbialdegradation.
 11. A seed germination medium according to claim 2 whereinthe upper and lower layers are bonded together by means of an adhesive.12. A seed germination medium according to claim 11 wherein the adhesivepermeates the upper layer and provides waterproofing properties to theupper layer.
 13. The seed germination medium of claim 1, wherein saidupper layer is a membrane and further comprising, beneath the upperlayer, at least one biological agent for encouraging plant developmentand/or breaking down the upper layer and/or lower layer.
 14. A seedgermination medium according to claim 13 wherein the biological agentsare microbial species selected from bacteria and fungi.
 15. A seedgermination medium according to claim 13 wherein the biological agentsare capable of degrading polysaccharides such as cellulose and starch.